When humans abandon an area because of an international treaty, what becomes of the land?

The Green Line, Cyprus

The Green Line, Cyprus

Where: Running east-west across the island of Cyprus, roughly dividing it into northern and southern halves.

Size: 112 miles long, up to 4.6 miles wide

Why It Exists: The island of Cyprus has a mixed population of ethnic Greeks and Turks. When the government was toppled in 1974 by a pro-Greek coup, there were fears that the new government would seek unification with Greece, against the wishes of Turkish Cypriots. The Turks invaded and the island was effectively split in two, with Turkish Cypriots in the north and Greek Cypriots in the south, separated by a U.N. buffer zone.

What It's Like Now: While there are some 10,000 people living in the zone, much of it is deserted and has been reclaimed by nature. An estimated 300 mouflon (a kind of wild sheep with curved horns) roam freely in the only place on the island where hunters cannot touch them. The Green Line, then, is a good example of what scientists call an "involuntary park"—a place that humans abandoned or where the human population diminished for other reasons, such as to create a DMZ, leaving a void where flora and fauna could thrive without human interference.

Iraq–Kuwait Border

Iraq–Kuwait Border

Where: The boundary between Iraq and Kuwait

Size: 120 miles long, 1 km (1100 yards) wide

Why It Exists: Saddam Hussein did not invent the dispute between Iraq and Kuwait, which has deep historical roots. Some Iraqis believe that Kuwait belongs to Iraq, and neither the 1991 Persian Gulf War nor the 2003 Iraq War settled the question. It was only in 2010 that the Iraqi government officially agreed to recognize the border. The area within 500 meters of the border on either side has been cleared to create a DMZ.

What It's Like Now: Although the land is dry, there were many farms along the border and Iraqi farmers are trying to get compensation from the government for lost harvest and water wells. Earlier this year Kuwait requested that the U.N. repair some of the border markers, but the Iraqis have objected that the new border will cut through more of their farms. In 2011 Iraqi Shiite militia threatened to attack Kuwait’s new Mubarak port, which they say threatens Iraq’s access to the sea, and rockets were fired in the border area.